So far, for the small and medium-sized electric contacts, contact materials with good electroconductivity comprising gold, gold alloy, silver and silver alloy have been used because of low contacting force. With these contact materials, however, when the number of works of switching-on and -off increases, the exhaustion reaches the substrate metal because of low hardness (Hv 100-200) and low melting point (900.degree.-1060.degree. C.) resulting in the scattering of exhausted powder onto the surface of contact. Hence, the contacting resistance etc. increased leading to the instability. Moreover, the time-lag (poor restoration) was caused due to the adherence and locking of the surface of contact leading to a drawback of remarkably short life of contact. On the other hand, in the cases of lead switch etc., if using W, Mo, etc. being metals with high melting point from the reasons of low contacting pressure and difficulty in providing thick layer of contact, the increase in the contacting resistance cannot be prevented. So, plated contacts with noble metals such as Rh, Ru, etc. are broadly used.
However, the Rh contact has a drawback that the contacting resistance increases with organic gases containing in the atmosphere and organic gases previously adsorbed onto the surface. Moreover, it is impossible to give the plating onto easily oxidizable contact strips or lead pieces of Fe, Ni, etc. and it is required to plate intervening plated layers of Au, Ag, Cu, etc. For this reason, effective plating thickness decreases and the process becomes complicated on production leading to a drawback of high-processing price for contact. Disclosure of the invention
As a result of extensive investigations in view of this situation, low-cost electric contact materials, wherein said drawbacks were solved and the life of contact and reliability were improved, production methods thereof and electric contacts used these have been developed according to the invention.
Namely, the first of the inventive materials is characterized in that a covering layer having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed on the substrate as an electric contact in a thickness of 0.03 to 100 .mu.m.
Moreover, the second of the inventive materials is characterized in that, in the middle of substrate and 0.03 to 100 .mu.m thick covering layer of electric contact being the outermost layer and having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient, a not less than 0.1 .mu.m thick intermediate layer having a composition of ABx (A: transition metal of group IVa, Va or VIa, B: carbon, nitrogen, boron, silicon or aluminum) and having a gradient composition of X=0 on the side of substrate and X=1 in cases of carbon and nitrogen, X=2 in cases of boron and silicon and X=3 in case of aluminum on the side of covering layer of electric contact is formed.
Furthermore, the third of the inventive materials is characterized in that an intermediate layer comprising soft metal is covered on the substrate in a thickness of not less than 0.01 .mu.m and, thereon, a covering layer of electric contact having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed in a thickness of 0.03 to 100 .mu.m.
And, as said intermediate layer comprising soft metal, use of a metal having at least one selected from Ag, Al, Au, Co, Cu, Fe, Mg, Ni, Pd, Pt, Sr, Cr and transition metals of groups IVa and Va as a major ingredient is effective, and, in this case, as the transition metal for forming the intermediate layer, use of the same kind of transition metal as that constituting carbide, nitride, boride, silicide or aluminide to be formed thereon is also effective.
Further, in both cases aforementioned, as the covering layer of electric contact, constitution of two or more layers layered the materials selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa brings about good effect.
Still more, the fourth of the inventive materials is characterized in that a 0.03 to 100 .mu.m thick intermediate layer having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is provided on the substrate as an electric contact and, thereon, a not less than 0.01 .mu.m thick surface layer comprising soft metal is formed. Also, in this case, use of a soft metal having at least one selected from Ag, Al, Au, Co, Cu, Fe, Mg, Ni, Pd, Pt, Sr, Cr and transition metals of groups IVa and Va as a major ingredient for surface layer is effective, and the layering of two or more layers of materials selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa is effective constitution as an intermediate layer.
And, as the transition metal of group IVa to be used for the inventive electric contact materials described above, one having at least one selected from Ti, Zr and Hf as a major ingredient is good, as the transition metal of group Va, one having at least one selected from V, Nb and Ta as a major ingredient is good, and, as the transition metal of group VIa, one having at least One selected from Cr, Mo and W as a major ingredient is good.
Next, the first of the production methods of the inventive electric contact materials is characterized in that said covering layer as the electric contact having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed by plasma CVD in a thickness of 0.03 to 100 .mu.m, and, upon forming said covering layer by plasma CVD using said nitrides among those as raw materials, good results can be obtained when performing in such a way that, after the surface cleaning with ions or electrons, the plasma CVD is performed at a total pressure of 0.1 to 10 Torr while heating the substrate to 300.degree. to 900.degree. C. under an atmosphere flowing N.sub.2 gas and chloride gas of transition metal of group IVa, Va or VIa as raw material gases so as the flow ratio of both (N.sub.2 gas/chloride gas) to become not higher than 7 using hydrogen as a carrier gas.
Moreover, the second of the inventive production methods is characterized in that the covering layer as the electric contact having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed by sputtering in a thickness of 0.03 to 100 .mu.m, and upon forming said covering layer by sputtering using said nitrides among those as raw materials, it is effective to perform in such a way that, after the surface cleaning with ions or electrons, the sputtering is performed at a total pressure of 1 to 50 mTorr while heating the substrate to 300.degree. to 900.degree. C. under an atmosphere flowing Ar and N.sub.2 gas as gases in the reactor so as the flow ratio of both (N.sub.2 gas/(Ar+N.sub.2)gases) to become not lower than 0.1.
Furthermore, the third of the inventive production methods is characterized in that the covering layer as the electric contact having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed by ion assist vaporization in a thickness of 0.03 to 100 .mu.m, and, upon forming said covering layer by ion assist vaporization using said nitrides among those as raw materials, it is effective to perform in such a way that, after the surface cleaning with ions or electrons, the ion assist vaporization is performed at a total pressure of 10.sup.-3 to 10.sup.-6 Torr and at a ratio of N atom to transition metal atom reaching the unit area of substrate per unit time of N/transition metal&gt;2 while heating the substrate to 300.degree. to 900.degree. C. under an atmosphere being the gas pressure supplying to ion gun of N.sub.2 gas/(Ar+N.sub.2) gases&gt;0.1.
Still more, the fourth of the inventive production methods is characterized in that the covering layer as the electric contact having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed by ion plating in a thickness of 0.03 to 100 .mu.m, and, upon forming said covering layer by ion plating using said nitrides among those as raw materials, it is better to perform in such a way that, after the surface cleaning with ions or electrons, the ion plating is performed at a total pressure of 10.sup.-2 to 10.sup.-5 Torr and at a ratio of N atom to transition metal atom reaching the unit area of substrate per unit time of N/transition metal&gt;2 while heating the substrate to 300.degree. to 900.degree. C. under an atmosphere being the gas pressure supplying to ionization mechanism of N.sub.2 gas/(Ar+N.sub.2 ) gases.gtoreq.=0.1.
Still more, the fifth of the inventive production method is characterized in that the covering layer as the electric contact having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed by laser beam sputtering in a thickness of 0.03 to 100 .mu.m, and, upon forming said covering layer by laser beam sputtering using said nitrides among those as raw materials, it is more advantageous to perform in such a way that, after the surface cleaning with ions or electrons, the laser beam sputtering is performed while heating the substrate to 300.degree. to 900.degree. C. under an atmosphere flowing Ar and N.sub.2 gas as gases in the reactor so as the flow ratio of both (N.sub.2 gas/(Ar+N.sub.2)gases) to become not lower than 0.1.
Next, the first of the inventive electric contacts is characterized in that, in the electric contact comprising a pair of contacting portions A and B, each contacting portion is constituted by forming a film of contact having at least one of nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient on the substrate in a thickness of 300 .ANG. to 100 .mu.m.
Moreover, the second of the inventive electric contacts is characterized in that, in the electric contact comprising a pair of contacting portions, one contacting portion A is constituted by forming a film of contact having at least one of nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient on the substrate in a thickness of 300 .ANG. to 100 .mu.m and other contacting portion B is constituted by forming a film of contact having different material quality from that of contacting portion A on the substrate, and it is effective to form in a way that, as the contacting portion B, a single or multiplex-layered film of contact having at least one of nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa and being different from the material quality constituting the contacting portion A as a major ingredient is formed in a thickness of 300 .ANG. to 100 .mu.m, or in a way that, as the contacting portion B, a film of contact is formed with platinum group metal or alloy different from the material quality constituting the contacting portion A.
In following, foregoing each invention will be explained in detail.
In the first through third of the inventive materials, as described above, a covering layer of contact having at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa as a major ingredient is formed on the substrate plate as an electric contact with or without intermediate layer intervened. Besides, conventionally, the covering layer could not be coated directly onto the substrate plate and needed to be coated intervening the covering layers such as Au, Ag, Cu, etc. In the invention, however, the direct coating onto substrate has become possible using vapor phase method, in particular, chemical vaporization method or physical vaporization method because of the surface cleaning such as ion bombard or electron shower after the precise polishing such as electrolytic polishing for smoothing the surface of substrate.
Here, carbides, nitrides, borides, silicides and aluminides of said transition metals of groups IVa, Va and VIa, for example, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W have chemical stability, good environmental resistance (oxidation resistance, sulfurization resistance, etc.), high hardness and melting point, less transfer exhaustion, low wear and the like, thus they are excellent in the life for contact action and reliability and exhibit excellent properties as electric contacts.
With the inventive contact materials, if making the film thick, the contacting resistance would be 30 to 50 times-as high as that of Au or Ag within a range of practical contact pressure (load of below 30 g) and the thermal conductivity would also become low as ceramics. For this reason, in order to make the contacting resistance and the thermal conductivity as an electric contact a practically problem-free extent, the film was made thin to be 300 .ANG. to 100 .mu.m. If the thickness of film is under 300 .ANG., good electroconductivity cannot be obtained to increase the contacting resistance, the wear resistance is insufficient to give no enough life of contact, and the oxidation resistance also becomes insufficient. If the thickness of film is over 100 .mu.m, the contacting resistance increases to raise the temperature because of the roughening of surface due to coarsened crystals and the stabilized thermal conductivity cannot be obtained as well because of the thickening of film. Moreover, by layering the covering layer of contact in two or more layers, the decrease in pinholes in film and the compensation of characteristics become possible, thus effective. For the substrate of the inventive contact materials, Cu, Cu alloy, Fe alloy, Ni alloy, etc. are used.
Moreover, the intermediate layer shown in the second of the inventive materials is made so that the transition metal of covering layer of contact used is allowed to touch with the substrate, it inclines gradually to the composition of covering layer of contact, and it becomes finally the composition of covering layer of contact. In this way, metal elements touch mutually at the interface between substrate and intermediate layer and same compositions touch between intermediate layer and covering layer of contact leading to food affinity, improved adhesion and, at the same time, relaxation of stress in the covering layer of contact because of the gradient in the composition of intermediate layer. In addition, the difference in the thermal expansion between substrate and covering layer contact is relaxed and the occurrence of cracks in the covering layer of contact and peeling-off can be prevented.
Furthermore, through the layerings of substrate and intermediate layer and intermediate layer and covering layer of contact, the occurrence of pinholes is prevented. This intermediate layer has good electroconductivity and no problem of heat generation and effectively works for the improvement in the characteristics of contact. Moreover, because the intermediate layer is constituted with softer material than contact material, this decreases the substantial hardness of the layer of contact material and decreases the contacting resistance, thus the kinetic energy on closing circuit is relaxed with soft metal to decrease the chattering. And, along with the decreased chattering, the number of generations of chattering arc also decreases to enhance the life of contact portion. In addition, the error actions on throwing-in also remarkably decrease to effect the improved reliability. Further, through the formation of intermediate layer on the surface of substrate, the surface becomes smooth and the covered surface of contact also becomes smooth leading to low and stabilized contacting resistance, which is preferable from the characteristics of contact. The thickness of said intermediate layer is desirable to be not less than 0.1 .mu.m. This is because of that, if the thickness of film is under 0.1 .mu.m, the distribution of gradient composition ends up to be disturbed and the development of said effects ends up to become low. The upper limit of thickness is determined by the production cost, size of contact and distance between contacts.
For the substrate, use of Cu, Cu alloy, Fe alloy, Ni alloy, etc. is preferable.
Furthermore, in the third of the invention, an intermediate layer having at least one selected from Ag, Al, Au, Co, Cr, Cu, Fe, Mg, Ni, Pd, Pt, Sr and transition metals of groups IVa and Va as a major ingredient is covered on the substrate in a thickness of not less than 0.01 .mu.m, which improves the adhesion of covering layer of contact. As the intermediate layer, covering as it is may be good, but the diffusion treatment makes it more effective.
Through the provision of this intermediate layer, the stress in the covering layer of contact and the difference in the thermal expansion between substrate and covering layer of contact are relaxed together with the improved adhesion between substrate and covering layer of contact resulting in the prevention from cracks in the covering layer of contact and peeling-off. Moreover, because the intermediate layer is softer than the covering layer of contact, it decreases the substantial hardness of the layer of contact material and decreases the contacting resistance, thus the kinetic energy on closing circuit is relaxed at the intermediate layer to decrease the chattering. And, along with the decreased chattering, the number of generations of chattering are also decreases to enhance the life of contact portion. In addition, the error actions on throwing-in also remarkably decrease to improve the reliability. Further, through the formation of intermediate layer on the surface of substrate, the surface becomes smooth and the covered surface of contact also becomes smooth leading to low and stabilized contacting resistance, thus good characteristics of contact.
The reason why the thickness of intermediate layer was made to be not less than 0.01 .mu.m is because of that, if the thickness of film is under 0.01 .mu.m, lots of pinholes occur and the corrosion progresses from pinholes to increase the contacting resistance. The thickness of this intermediate layer is determined by the production cost, size of contact and distance between contacts.
And, the covering layer of contact has at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa, for example, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W as a major ingredient and exhibits good characteristics of excellent environmental resistance, high hardness and melting point, less transfer exhaustion and low wear. If layering two or more different layers on the intermediate layer, the decrease in the in-film pinholes of covering layer of contact and the compensation of characteristics become possible. This contact material exhibits good characteristics of excellent environmental resistance, high hardness and melting point, less transfer exhaustion and low wear.
Such covering layer of contact is formed by the chemical vaporization or physical vaporization and the thickness of film is made to be 0.03 to 100 .mu.m. If the thickness of film is under 0.03 .mu.m, good electroconductivity cannot be obtained to increase the contacting resistance, the wear resistance is insufficient to give no enough life of contact, and the oxidation resistance etc. also become insufficient. Moreover, if the thickness of film is over 100 .mu.m, the contacting resistance increases to raise the temperature because of the roughening of surface due to coarsened crystals and the stabilized thermal conductivity cannot be obtained as well because of the thickening of film. Besides, for the substrate of the inventive contact materials, Cu, Cu alloy, Fe alloy, Ni alloy, etc. are used.
Moreover, in the third of the inventive materials, the transition metal of thin film of contact used is provided on the substrate as an intermediate layer, thereby the affinity between substrate and thin film of contact is improved, the difference in thermal expansivity is made small, and, at the same time, the misfit of lattice constant can be made small. In this way, metals touch mutually at the interface between substrate and intermediate layer and some kinds lie between intermediate layer and thin film of contact leading to good affinity, improved adhesion and simultaneously relaxation of stress due to the difference in thermal expansion to prevent the damage of thin film of contact. Also, through the layering of substrate/intermediate layer/thin film of contact, the occurrence of pinholes is prevented. Further, because the lattice constant of transition metal of intermediate layer is close to that of carbide, nitride and diboride of transition metal, the misfit becomes small to permit good control of crystals. This intermediate layer has good electroconductivity and no problem of heat generation etc. and effectively works from the characteristics of contact. For the substrate, Cu, Cu alloy, Fe alloy, etc. are used.
Further, in the fourth of the inventive materials, the substantial hardness of contact portion was decreased and the contacting resistance was stabilized by providing further with a layer of soft metal on the surface of said covering layer of electric contact for improving the points that, although the electric contact with good characteristics can be obtained by decreasing the thickness of film of nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa, for example, Ti, Zr, V, Hf, Nb, Ta, Cr, Mo and W as the covering layer of electric contact to 300 .ANG. to 100 .mu.m, the initial contacting resistance of electric contact formed with these materials is unstable and the absolute value is slightly higher over the contact made of noble metals. In this way, the kinetic energy of contact is exhausted to some extent on the surface layer, thus the chattering, which occurs by elastically leaping up the contact portion, decreases to enhance the life of contact. In addition, the error actions on throwing-in accompanying with chattering remarkably decrease to improve the reliability. Moreover, the increased contacting area results in a low and stabilized contacting resistance, thus the characteristics of contact become good. The reason why the thickness of film on the surface layer was made to be not less than 100 .ANG. is because of that, if under 100 .ANG., defects of pinholes etc. are caused and the effects can hardly be seen.
As the material quality of this surface layer, at least one may be selected among Ag, Au, Co, Cr, Cu, Fe, Hf, Mg, Nb, Ni, Pd, Pt, Sr, Ta, Ti, V and Zr, if the facts that the hardness is lower than that of intermediate layer, the resistivity is not more than 50 .mu.m .OMEGA. cm, and the melting point is not less than 600.degree. C. are taken as criteria. Moreover, for the substrate, Cu, Cu alloy, Fe alloy, Ni alloy are used, and the intermediate layer and the surface layer are formed by physical vaporization or chemical vaporization and by physical vaporization, chemical vaporization or electrolytic plating, respectively.
And, in the fourth of said inventive materials, if the intermediate covering layer of contact has at least one selected from carbides, nitrides, borides, silicides and aluminides of transition metals of groups IVa, Va and VIa, for example, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W as a major ingredient, it exhibits good characteristics of excellent environmental resistance, high hardness and melting point, less transfer exhaustion and low wear. Further, if layering different materials in two or more layers, the decrease in the in-film pinholes in covering layer of contact and the compensation of characteristics become possible. This contact material exhibits good characteristics of excellent environmental resistance, high hardness and melting point, less transfer exhaustion and low wear.
In this case, the covering layer of contact being the intermediate layer is formed by chemical vaporization or physical vaporization and the thickness of thin film is made to be 0.03 to 100 .mu.m. If the thickness of film is under 0.03 .mu.m, good electroconductivity cannot be obtained to increase the contacting resistance, the wear resistance is insufficient to give no enough life of contact, and the oxidation resistance etc. become insufficient. Also, if the thickness of film is over 100 .mu.m, the contacting resistance increases to raise the temperature because of the roughening of surface due to coarsened crystals and the stabilized thermal conductivity cannot be obtained as well because of the thickening of film. Besides, for the substrate of the inventive contact materials, Cu, Cu alloy, Fe alloy, Ni alloy, etc. are used.
Moreover, in said electric contact materials, there are transition metals, for example, Ti, Zr and Hf for group IVa, for example, V, Nb and Ta for group Va and, for example, Cr, Mo and W for group VIa.
Next, with respect to the production methods of said inventive electric contact materials, it was made possible to make the characteristics of film, that is, hardness, specific resistance, color tone and composition ratio appropriate by forming the covering layer as said electric contact by plasma CVD method, sputtering method, ion assist vaporization method, ion plating method, laser beam sputtering method or the like.
And, by the prior arts, the covering layer of contact could not be coated directly onto the substrate, but required to be coasted intervening the covering layers of Au, Ag, Cu, etc. By the inventive production methods, however, direct coating of thin film of nitrides having at least one of transition metals of groups IVa, Va and VIa as a major ingredient onto the substrate has been made possible by performing the surface cleanings such as ion bombard, electron shower, etc. after the precise polishings such as electrolytic polishing etc. for smoothing the surface of substrate.
With respect to the forming method of thin film of nitrides in the first of the inventive production methods, as a result of diligent investigations on plasma CVD, following conditions were known to be indispensable in order to achieve the characteristics of film, that is, hardness, specific resistance, color tone, composition ratio of nitrogen to transition metal of group IVa, Va or VIa, etc.
Namely, the total pressure in the reactor on forming thin film is appropriate to be 0.1 to 10 Torr, and, using hydrogen gas as a carrier gas, the thin film of nitrides may be formed while heating the substrate to 300.degree. to 900.degree. C. under an atmosphere using nitrogen gas and chloride gas having at least one of transition metals of groups IVa, Va and VIa as a major-ingredient for raw material gases at a flow ratio of not higher than 7. At this time, for generating plasma, either high-frequency discharge or direct current discharge is used.
Moreover, in the second of the inventive production methods, following conditions are required in order to achieve the characteristics of film, that is, hardness of film, specific resistance, color tone, desired composition ratio of nitrogen to at least one of transition metals of groups IVa, Va and VIa, etc. on forming thin film of said nitrides by sputtering. Namely, making the total pressure in reactor on forming thin film to be 1 to 50 m Torr, the thin film of nitrides may be formed while heating the substrate plate to 300.degree. to 900.degree. C. under an atmosphere being the flow ratio of gases at a ratio of N.sub.2 /(Ar+N.sub.2).gtoreq.0.1. At this time, DC or RF is used for sputtering.
Further, as the film-forming method on forming the surface layer having at least one of nitrides of transition metals of groups IVa, Va and VIa as a major ingredient on the substrate by ion assist vaporization in the third of the inventive production methods, such an equipment that, as shown in FIG. 1, an unwinding mechanism (3) and a winding mechanism (4) of substrate (2) are provided in chamber (1), an ion gun (5) irradiating nitrogen ion onto the substrate (2) and an evaporation source (6) of transition metal are installed on one side, and a heating device (7) of substrate is attached to the other side may be used. Besides, for the exhaust inside the chamber (1), both rotary pump (8) and cryopump (9) are installed and further two auxiliary exhaust systems (10) are connected. Moreover, said equipment is optional in performing continuous coating or fixing for every batch depending on the shape of substrate, but, in the case of continuous coating, said unwinding mechanism and winding mechanism may be utilized.
The thin film of nitrides may be formed by ion assist vaporization method using said equipment. At this time, the evaporation rate of transition metal of group IVa, Va or VIa is appropriate to be 0.5 .ANG./s to 1000 .ANG./s and, making the total pressure to be 10.sup.-3 to 10.sup.-6 Torr and the ratio of number of N atoms (N) to number of atoms of transition metal (T) reaching the unit area of substrate per unit time to be 2&lt;N/T under an atmosphere being the bases supplying to ion gun at a ratio of N.sub.2 /(Ar+N.sub.2).gtoreq.0.1 and further heating the substrate to 300.degree. to 900.degree. C., coating is made, thereby good characteristics can be achieved.
Moreover, as the heating method of evaporation source, heating by electron beam is common, but the film formation is possible similarly by ion beam sputtering and laser ablation with inert gas ions such as Ar etc.
Moreover, as the film-forming method on forming the surface layer having at least one of nitrides of transition metals of groups IVa, Va and VIa as a major ingredient on the substrate by ion plating in the fourth of the inventive methods, such an equipment that, as shown in FIG. 2, an unwinding mechanism (3) and a winding mechanism (4) of substrate (2) are provided in chamber (1), an evaporation source (6) and an ionizing mechanism (11) ionizing nitrogen are installed on one side, and a heating device (7) of substrate is attached to the other side may be used. Besides, for the exhaust inside the chamber (1), both rotary pump (8) and cryopump (9) are installed and further two auxiliary exhaust systems (10) are connected. Moreover, said equipment is optional in performing continuous coating or fixing for every batch depending on the shape of substrate, but, in the case of continuous coating, said unwinding mechanism and winding mechanism may be utilized.
The thin film of nitrides may be formed by ion plating method using said equipment. At this time, the evaporation rate of transition metal of group IVa, Va or VIa is appropriate to be 0.5 .ANG./s to 1000 .ANG./s and, making the total pressure to be 10.sup.-2 to 10.sup.-5 Torr and the ratio of number of N atoms (N) to number of atoms of transition metal (T) reaching the unit area of substrate per unit time to be 2&lt;N/T under an atmosphere being the gases supplying to ionizing mechanism at a ratio of N.sub.2 /(Ar+N.sub.2).gtoreq.0.1 and further heating the substrate to 300.degree. to 900.degree. C., coating is made, thereby good characteristics can be achieved.
Moreover, as the heating method of evaporation source, heating by electron beam is common, but the film formation is possible similarly by ion beam sputtering and laser ablation with inert gas ions such as Ar etc.
Further, in the forming method of thin film of nitrides in the fifth of the inventive production methods, as a result of diligent investigations on the laser beam sputtering method, following conditions are known to be indispensable in order to achieve the characteristics of film, that is, hardness, specific resistance, color tone, given composition ratio of nitrogen to transition metal of group IVa, Va or VIa, etc.
Namely, in the reactor on forming thin film, making the flow ratio of nitrogen gas to argon gas as an atmosphere to be N.sub.2 /(Ar+N.sub.2).gtoreq.0.1, the thin film of nitrides is formed while heating the substrate to 300.degree. to 900.degree. C.
And, by using short-wavelength laser beam irradiation, ultraviolet ray irradiation or RF plasma-excitation, good effects are further exerted on the lowering of substrate temperature and the crystal characteristics of thin film.
Next, as the first of the inventive electric contacts, the electric contact having good characteristics can be obtained by decreasing the thickness of film of nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa, for example, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W to be 300 .ANG. to 100 .mu.m. However, for improving the life characteristic further, the problem of adherence cannot be neglected. There, in the second of the inventive electric contacts, one contacting portion A is formed with at least one of nitrides, carbides, silicides, diborides and aluminides of transition metals of IVa, Va and VIa making it as a major ingredient and the contacting portion B opposing thereto is formed with different material quality from said contacting portion A, for example, with at least one of nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa different from nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa forming the contacting portion A making it as a major ingredient, or the film of contact is formed with platinum group metal or alloy, thus obtaining hardly adherent electric contact.
Besides, for the substrate, Cu, Cu alloy, Fe alloy, Ni alloy, etc. such as 52% Ni-Fe alloy (52 Alloy), phosphor bronze, etc. are used. For forming nitrides, carbides, silicides, diborides and aluminides of transition metals of groups IVa, Va and VIa on the substrate, vaporization, ion assist vaporization from gas ion source, ion assist vaporization from solid ion source, sputtering, laser beam sputtering, CVD, etc. are used and, for forming platinum group metal or alloy, said physical vaporization, chemical vaporization or electrolytic plating is used. Moreover, for the pretreatment of substrate before vaporization or electrolytic plating, electrolytic polishing and ion bombard treatments are carried out after the organic cleaning, thereby the thermal shock resistance is enhanced.